An Investigation of Simple Evaporation Models Used in Spray Simulations

2003 ◽  
Vol 125 (1) ◽  
pp. 179-182 ◽  
Author(s):  
G. F. Yao ◽  
S. I. Abdel-Khalik ◽  
S. M. Ghiaasiaan
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Numerical Solutions ◽  
Film Theory ◽  
Mass Transfer Rate ◽  
High Mass ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
Model Predictions ◽  
Evaporation Models

In the present work, an unified derivation of simple evaporation models used in spray simulation is described and a new evaporation model is formulated. In the model, the Nusselt number, Sherwood number, and evaporation mass flux are derived using the traditional film theory. However, instead of determining the film thicknesses using the Nusselt and Sherwood numbers derived in the absence of high mass transfer rate, the film thicknesses are calculated from those derived from the fully numerical solutions which represent the realistic heat and mass transfer processes around a droplet. The model predictions are compared with the fully numerical solutions.

scholarly journals SWSex Stars, Old Novae, and the Evolution of Cataclysmic Variables

2015 ◽  
Vol 2 (1) ◽  
pp. 188-191 ◽  
Author(s):  
L. Schmidtobreick ◽  
C. Tappert
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Cataclysmic Variables ◽  
High Mass ◽  
Period Range ◽  
Transfer Rates ◽  
Low Mass ◽  
Orbital Periods ◽  
Nova Outburst

The population of cataclysmic variables with orbital periods right above the period gap are dominated by systems with extremely high mass transfer rates, the so-called SW Sextantis stars. On the other hand, some old novae in this period range which are expected to show high mass transfer rate instead show photometric and/or spectroscopic resemblance to low mass transfer systems like dwarf novae. We discuss them as candidates for so-called hibernating systems, CVs that changed their mass transfer behaviour due to a previously experienced nova outburst. This paper is designed to provide input for further research and discussion as the results as such are still very preliminary.

scholarly journals Numerical Investigation of Natural Convective Condensation with Noncondensable Gases in the Reactor Containment after Severe Accidents

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Wen Fu ◽  
Li Zhang ◽  
Xiaowei Li ◽  
Xinxin Wu
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Mass Fraction ◽  
Transfer Processes ◽  
Noncondensable Gases ◽  
Mass Transfer Processes ◽  
Convective Condensation

The heat and mass transfer processes of natural convective condensation with noncondensable gases are very important for the passive containment cooling system of water cooled reactors. Numerical simulation of natural convective condensation with noncondensable gases was realized in the Fluent software by adding condensation models. The scaled AP600 containment condensation experiment was simulated to verify the numerical method. It was shown that the developed method can predict natural convective condensation with noncondensable gases well. The velocity, species, and density fields in the scaled AP600 containment were presented. The heat transfer rate distribution and the influences of the mass fraction of air on heat transfer rate were also analyzed. It is found that the driving force of natural convective condensation with noncondensable gases is mainly caused by the mass fraction difference but not temperature difference. The natural convective condensation with noncondensable gases in AP1000 containment was then simulated. The temperature, species, velocity, and heat flux distributions were obtained and analyzed. The upper head of the containment contributes to 35.1% of the total heat transfer rate, while its area only takes 25.4% of the total condensation area of the containment. The influences of the mass fraction of low molecular weight noncondensable gas (hydrogen) on the natural convective condensation were also discussed based on the detailed species, density, and velocity fields. The results show that addition of hydrogen (production of zirconium-water reaction after severe accident) will weaken the intensity of natural convection and the heat and mass transfer processes significantly. When hydrogen contributes to 50% mole fraction of the noncondensable gases, the heat transfer coefficient will be reduced to 45%.

scholarly journals MASS TRANSFER CORRELATION FOR THE REMOVAL OF COPPER IONS FROM WASTEWATER

2010 ◽  
Vol 9 (1-2) ◽  
pp. 63
Author(s):  
N. M. S. Kaminari ◽  
M. J. J. S. Ponte ◽  
H. A. Ponte
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Copper Ions ◽  
Mass Transfer Rate ◽  
Reynolds Numbers ◽  
Electrochemical Reactor ◽  
High Mass ◽  
Ore Processing ◽  
Lead Nickel ◽  
Copper Lead

One of the biggest problems with ore processing in extractive metallurgical industries is the high toxicity of the heavy metals waste content (e.g., copper, lead, nickel and chrome). This work investigates the copper (II) íons removal from aqueous solutions in concentrations up to 1000 ppm. Therefore, a fluidized bed electrolytic reactor was used with flow-by configuration considered as a hopeful method due to the large specific surface area and the high mass transfer rate. The performance of the electrochemical reactor was investigated by using different porosities. Dimensionless Sherwood and Reynolds numbers were correlated to characterize the mass transport properties of the reactor, and they were fitted to the equation Sh = a.Reb.Sc1/3.

Examples of Microchannel Mass Transfer Processes in Biological Systems

2003 ◽  
Author(s):  
Satish G. Kandlikar ◽  
Mark E. Steinke
Keyword(s):  
Mass Transfer ◽  
Biological Systems ◽  
Molecular Transport ◽  
Transport Processes ◽  
Artificial Organs ◽  
High Mass ◽  
Transfer Coefficients ◽  
Natural Systems ◽  
Transfer Processes ◽  
Mass Transfer Processes

Heat and mass transfer processes become highly efficient as the channel hydraulic diameter is reduced in size. Biological systems, such as human body, rely on the extremely efficient transport processes occurring at microscale in the functioning of its vital organs. In this paper, the transfer processes in lungs and kidneys will be reviewed. Although the flow in the microchannels present in these organs is laminar, it yields very high mass transfer coefficients due to the coupling of small channel diameters. Furthermore, the molecular transport mechanisms occurring across the membranes at nanoscales through diffusion controlled processes also become extremely important. Understanding these transport processes will enable us to develop more efficient artificial organs and processes that closely mimic the performance of the natural systems. These ideas can be extended to other microscale system designs in different technologies, such as IC cooling and MEMS micro fuel cells.

scholarly journals Liquid-Liquid Equilibrium of Deep Eutectic Solvent-Aromatic-Aliphatic Ternary Systems: Experimental Study with COSMO Model Predictions

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1169
Author(s):  
Kyle McGaughy ◽  
M. Toufiq Reza
Keyword(s):  
Mass Transfer ◽  
Hydrogen Bond ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Transfer Coefficients ◽  
Liquid Equilibrium ◽  
Mass Transfer Coefficients ◽  
Cosmo Model ◽  
Lower Accuracy ◽  
Model Predictions

Common solvents used for aromatic extraction from aliphatics typically degrade into toxic compounds, while green alternatives perform poorly compared to the state-of-the-art solvents. Deep eutectic solvents (DES) are a novel solvent type made of hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA). DES have been applied in various applications, including advanced separations. In this study, DES were studied experimentally and using the Conductor-like Screening Model (COSMO) to separate benzene from cyclohexane as model compounds for an aromatic:aliphatic system. Both equilibrium and kinetic studies were performed to determine the liquid liquid equilibrium (LLE) and mass transfer rate for the DES-based separation. Selected HBAs including tetrabutylammonium bromide (N4444Br), tetrahexylammonium bromide (N6666Br), choline chloride (ChCl), and methyltriphenylphosphonium bromide (METPB) were paired with HBDs including ethylene glycol (EG) and glycerol (Gly). COSMO was used, with adjustments to reflect DES specific interactions, to predict the liquid-liquid equilibrium (LLE). COSMO results showed that ChCl and N6666Br-based DES extracted too little benzene or too much cyclohexane, respectively, to be considered for experimental evaluation. Overall, the COSMO model predictions for LLE of EG-based DES were very accurate, with root-mean-square deviations (RMSD) below 1% for both N4444Br:EG and METPB:EG. The glycerol systems were less accurately modeled, with RMSD’s of 4% for N4444Br:Gly and 6% for METPB:Gly. The lower accuracy of glycerol system predictions fmay be due to limitations in COSMO for handling glycerol’s influence on polarizability in the DES that is not seen in EG-based DES. Mass transfer kinetics were determined experimentally for DES and the results were fit to a first order kinetics model. METPB:Gly had the highest mass transfer coefficient at 0.180 min−1, followed by N4444Br:EG at 0.143 min−1. N4444Br:Gly and METPB:EG had the lowest mass transfer coefficients at 0.096 min−1 and 0.084 min−1, respectively. It was found that mass transfer rate was not directly related to maximum benzene solubility, as N4444Br:EG and METPB:Gly had the highest and lowest benzene removal, respectively, but had similar mass transfer coefficients.

scholarly journals BC Cassiopeiae: First detection of IW Andromedae-type phenomenon among post-eruption novae

2020 ◽  
Vol 72 (6) ◽  
Author(s):  
Taichi Kato ◽  
Naoto Kojiguchi
Keyword(s):  
Mass Transfer ◽  
White Dwarf ◽  
Transfer Rate ◽  
White Dwarfs ◽  
Mass Transfer Rate ◽  
Cataclysmic Variables ◽  
High Mass ◽  
Average Mass ◽  
Classical Nova ◽  
Decline Rate

Abstract IW And-type dwarf novae are a recently recognized group of cataclysmic variables which are characterized by a sequence of brightening from a standstill-like phase with damping oscillations often followed by a deep dip. We found that the supposed classical nova BC Cas which erupted in 1929 experienced a state of an IW And-type dwarf nova in 2018, 89 yr after the eruption. This finding suggests that a high mass-transfer rate following the nova eruption is associated with the IW And-type phenomenon. The mass of the white dwarf inferred from the decline rate of the nova is considerably higher than the average mass of the white dwarfs in cataclysmic variables, and these massive white dwarfs may be responsible for the manifestation of the IW And-type phenomenon.

Highly Accelerated Compressible Laminar Boundary Layer Flows With Mass Transfer

1971 ◽  
Vol 93 (3) ◽  
pp. 281-289 ◽  
Author(s):  
A. Wortman ◽  
A. F. Mills
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Laminar Boundary Layer ◽  
Transfer Rate ◽  
Numerical Solutions ◽  
Mass Transfer Rate ◽  
Solution Procedure ◽  
Boundary Layer Flows ◽  
Displacement Thickness ◽  
Simplifying Assumptions

Exact numerical solutions have been obtained for highly accelerated self-similar laminar boundary layer flows with and without mass transfer. Values of the acceleration parameter β in the range 0 to 20 were considered. Variable gas properties were realistically modeled by assuming ρ ∝ h−1, μ ∝ hω, and Pr = constant. The results presented show the dependence of wall shear stress, heat transfer rate, and displacement thickness on the problem parameters which include β, Mach number, wall enthalpy ratio, mass transfer rate, ω and Pr. The inadequacy of solutions obtained under the simplifying assumptions of Pr = 1.0 and ω = 1.0 is clearly displayed. The numerical solution procedure employed proved quite adequate for a class of problem which has presented serious difficulties to previous investigators.

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